Selenium rectifier



Feb. 2s, l195o A, M SERLE 2,498,714

SELENIUM RECTIFIER Filed Aug. 2` 1946 INVENTOR ARTHU M. SEA/W E L (MM ATTORNEY menaa Feb. 2s, 195o l SELENIUM nEcmTEa Arthur Mackenzie Searle, London, England, alsignor to International Standard Electric Corporation, New York, N. Y.

Application August 2, 1946, Serial No. 687.873

In Great Britain July 20, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires July 20. 1965 2 Claims. l

This invention relates to electrically asymmetric devices such as rectiners, photoelectric cells and thermo-couples of the dry contact type and more particularly to those using a coating of selenium for the semi-conducting layer.

Selenium coated elements such as are ordinarily used for rectiilers, photoelectric cells and thermo-couples usually comprise a metal base plate which may be of iron, steel or aluminium, the surface of which is suitably prepared to receive a semi-conducting layer and may be coated with another substance such as nickel. A layer or coating of semi-conducting material such as selenium or a compound containing selenium is spread over the surface of such a base plate, for example. by fusingthe material or condensing the vapour thereof or by compressing a layer of powdered material at elevated temperature. It has also been known to provide such a layer by electro-deposition. A base plate, so coated, is then ordinarily treated further by heat to produce the proper crystal structure in the selenium or compound and may be given a further treatment to adapt it as a rectifier or a photoelectric cell. For instancea counter electrode may be applied over the surfaceof the layer, for example, by spraying it with a`conducting substance such as Woods metal and it may then be given an electro-forming treatment by the application of a 'voltage between the base plate and counter-electrode.` According to the invention the metal base plate may be dispensed with and the element may be stiffened or reinforced by means of a nonconducting or electrically inert material such as Another feature of the invention consists. in a dry contact type electrically asymmetric element comprising a non-conducting material with wholly embedded in or impregnated with semi-conducting material with which two electrodes make contact.

` or projections whereby the element may be supported and aillxed. It may also be desirable that one or both of the electrodes extend over one` or more such projections to facilitate electrical connection thereto.

These and other features of the invention will be more clearly understood from the following description which taken in conjunction with the drawings, particularly describes and ascertains the nature of the invention.

In the drawings Fig..l is a sectional view of an element according to one embodiment of the invention.

Fig. 2 is a sectional view of an element according to another embodiment of the invention and Fig. 3 is a plan view of an element. Referring now to Fig. l, I is a plate of non-conducting material, such as ceramic, of suitable size and shape. 2 is a nickel or zinc coating applied to the surface of plate I by electro-plating or other suitable means and which extends over the edges 5, 5' of the plate for a purpose to be described later. A layer 3 of semi-conductor such as selenium is applied to the surface of 2 in well known manner and treated by heat or heat and pressure to bring it to the right state of conductivity. A counterelectrode 4 of low melting-point alloy is applied to the surface of 3. Electrical contact may be made to the element at the edges 5, 5' of the plate and the surface of the counter electrode l. If desired, the nickel coating 2 may be applied also to the back side 6 of the plate I to assist in making electrical contact therewith.

In Figure 2 a perforated ceramic plate I0 is encased in selenium II by dipping, for example, in molten selenium at a controlled temperature such that the viscosity of the liquid allows surplus selenium to draw off leaving a thin continuous skin over the ceramic, the perforations of which are also filled with selenium. Suitable heat or heat and pressure treatments are applied to bring the selenium to the required state of conductivity. A metal back electrode I3, formed of, say, nickel, zinc, copper, aluminium or any alloy thereof, is applied to one side of the plate by, for instance, spraying or vapourising. If 'desired, this operation may be performed before the heat and pressure treatments before mentioned. On the other side of the plate a counter electrode I2 of low melting point alloy, such as Woods metal, is applied by spraying. The ele- 55 ment so formed may be subjected to an electr@- forming process to improve its rectifying properties.

In Fig. 3 an element is shown of similar general construction to that in Fig. 2 but with the addition of a supporting limb 2i and two contact limbs 22, 23, these three limbs being part of the perforated ceramic plate 20. The plate 20 is dipped in molten selenium as far as the line A-A. The back electrode 24, extends down the back o! the limb 22 while the counter-electrode extends down the front oi limb 23 so that electrical contact may be -made to the elements through 22 and 23 while limb 2| may be used solely for supporting the element. If desired, however, the three limbs 2l, 22, 23, may be combined with one limb. in an obvious manner. with the back electrode extending down one side and the counter-electrode extending' down the other4 side. Furthermore the supporting limb 2i may be dispensed with and the element may be supported from 2.2 or 23 which may contain holes or insertstherefore or for connection purposes.

The perforated plate ill in Fig. 2 or the plate 20 in Fig. A3 may conveniently be replaced by woven or otherwise porous material, il desired, capable of being impregnated by selenium sufficiently to form a continuous semi-conductor from the back-electrode to the counter-electrode.

What is claimed is:

1. A selenium rectifier element that comprises a perforate ceramic supporting member, selenium coating said member and illling the perio- 4 rations thereof, a metallic bath electrode overlying and making contact with a ilrst part of the selenium coating and a counter-electrode overlying and making electrical contact with another and second part of said selenium coating. 2. A 'selenium rectifier element that comprises a foraminous ceramic plate ot substantially regular outline having an outwardly extending supyporting lug integrally formed therewith, a coating of selenium on said member filling the openings therein, a back electrode overlying a tlrst portion of the selenium coating and making electrical contact therewith and a counter-electrode overlying a second and diilerent portion of the selenium coating in electrical contact therewith.

ARTHUR MACKENZIE SEARLE REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

1. A SELENIUM RECTIFIER ELEMENT THAT COMPRISES A PERFORATE CERAMIC SUPPORTING MEMBER, SELENIUM COATING SAID MEMBER AND FILLING THE PERFORATIONS THEREOF, A METALLIC BATH ELECTRODE OVERLYING AND MAKING CONTACT WITH A FIRST PART OF THE SELENIUM COATING AND A COUNTER-ELECTRODE OVERLYING AND MAKING ELECTRICAL CONTACT WITH ANOTHER AND SECON PART OF SAID SELENIUM COATING. 